In theory: yes, with the right R6. In practice, you will need a slightly different solution.
To reset the EPS8266, REST needs to be pulled below Vcc/4 (usually ~0.8V). It has an internal weak pull-up and most pre-made modules (D1, NodeMCU, etc) add another external pull-up to avoid spurious resets.
Your photoresistor is probably over 1MΩ in the dark and in the 10..100kΩ range in light (measure!). Between Vcc and REST, it acts like another, variable pull-up. To pull the device into reset, you need to choose R6 low enough to overcome all these pull-ups, while at the same time keeping it high enough to avoid spurious resets. In practice, this won't work.
What you could do instead is using a Schmitt trigger (e.g. 74AC14), voltage comparator (with open collector, e.g. LM393) or OpAmp to monitor the voltage divider and use their output to pull REST to GND when it's dark.
As an alternative, I would suggest that you use the CH_PD (ENABLE) pin. Instead of the permanent 10k pull-up (R1), use the same voltage divider and select R6 to be around 3-4 times the 'light' resistance of your phototransistor. This should work without any additional parts. The only drawback is that you can't use the RTC memory as technically your device is off, not sleeping.
PS: To those not familiar with the ESP8266, the 'wake up' is actually a reset (usually triggered by the RTC pulling the reset line low) and the device has to be re-initialized after wake up.